Systems and methods for generating hydrogen from hycrocarbon fuels

a technology of hydrocarbon fuel and system, which is applied in the direction of hydrogen separation using solid contact, chemical apparatus and processes, chemical/physical processes, etc., can solve the problems of metal sulfides being less stable at high reforming temperatures, using sulfur-laden hydrocarbon fuels, and catalysts becoming ineffective by coke accumulation

Inactive Publication Date: 2005-10-20
NU ELEMENT
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  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The main issue that has prevented the use of sulfur-laden hydrocarbon fuels in fuel processors for hydrogen generation has been catalyst deactivation by coke deposition and by metal sulfide formation.
The catalyst then becomes ineffective by coke accumulation.
Those metal sulfides are less stable at the high reforming temperatures.
This method cannot be used to reform heavier hydrocarbon fuels, or even natural gas, when the fuel stream contains some level of hydrocarbons heavier than methane, because those fuels react to form coke at the temperatures required for the noble metal catalysts to become sulfur-tolerant.
Although the sulfur content in transportation fuels is approximately 500 ppm and logistic fuels could contain up to 1% sul...

Method used

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  • Systems and methods for generating hydrogen from hycrocarbon fuels
  • Systems and methods for generating hydrogen from hycrocarbon fuels

Examples

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example i

[0035] The system of FIG. 1 is operated with a logistic diesel fuel as feed. The molecular weight of the fuel is 220 gm / mole, the molecules contain on average 16 carbon atoms each, and their hydrogen to carbon ratio is 1.8. The sulfur content of the fuel is one percent by weight. The flow rate of stream 100 is adjusted relative to stream 114 so that the number of moles of water in stream 104 is three times the number of atoms of carbon in stream 114. The fuel is completely converted to hydrogen and carbon oxides in reaction zones 118 and 120. The flow rate of stream 122 is adjusted to be equal to the flow rate of stream 126. Stream 116 contains then 340 moles of hydrogen per atom of sulfur, and 4 moles of water per atom of carbon.

[0036] The temperature of reaction zone 118 is set to 500° C. The active metal in the catalyst is iridium. According to the teachings of U.S. Pat. No. 3,441,395 of Dent et al., no coke is formed when the number of moles of water per carbon atom fed to the ...

example ii

[0037] The system of FIG. 1 is operated with a low-sulfur diesel fuel as feed. The molecular weight of the fuel is 220 gm / mole, the molecules contain on average 16 carbon atoms each, and their hydrogen to carbon ratio is 1.8. The sulfur content of the fuel is fifteen parts per million by weight. The flow rate of stream 100 is adjusted relative to stream 114 so that the number of moles of water in stream 104 is three times the number of atoms of carbon in stream 114. The fuel is completely converted to hydrogen and carbon oxides in reaction zones 118 and 120. The flow rate of stream 122 is adjusted to be equal to one percent the flow rate of stream 126. Stream 116 contains then 4400 moles of hydrogen per atom of sulfur, and 3 moles of water per atom of carbon. The temperature of reaction zone 118 is set to 500° C. The active metal in the catalyst is rhodium. Predominance diagrams indicate that for a Rh catalyst the metallic form predominate over the metal sulfide when the catalyst op...

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Abstract

The present invention provides a system and a method to reform hydrocarbon fuels, including sulfur-laden liquid fuels, to produce a reformate stream containing hydrogen. The system comprises a reforming reactor using a hydrocarbon stream and a water stream as reactants. The water stream is mixed with a hydrogen-rich stream prior to mixing with the hydrocarbon stream and fed to the reforming reactor, which contains a precious metal based catalyst. In one embodiment of the present invention, the temperature of the catalyst is lower at the inlet to prevent formation of coke by pre-reforming heavy hydrocarbons to methane, and higher at the outlet for efficient production of hydrogen. In another embodiment, air is introduced periodically into the system to burn off any metal sulfides and coke deposits that could form. In another embodiment, pure hydrogen is separated from the reformate stream using a hydrogen selective, sulfur-tolerant membrane or by pressure swing adsorption. Thus, the system and method of the present invention can be used to process sulfur-laden, heavy hydrocarbons to produce PEM fuel-cell quality hydrogen.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 60 / 541,128 , filed Feb. 3, 2004, which application is hereby incorporated by reference.FIELD [0002] The present invention relates to systems and methods for producing hydrogen from a hydrocarbon fuel. BACKGROUND [0003] The main issue that has prevented the use of sulfur-laden hydrocarbon fuels in fuel processors for hydrogen generation has been catalyst deactivation by coke deposition and by metal sulfide formation. [0004] Coke forms readily when heavy hydrocarbon fuels are heated to the high reforming temperatures required for efficient hydrogen production. The catalyst then becomes ineffective by coke accumulation. In U.S. Pat. No. 3,441,395, Dent et al., incorporated by reference, taught the use of a two-stage reformer, with a first stage operating at lower temperatures than the second stage, to avoid coke formation when reforming liqu...

Claims

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Application Information

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IPC IPC(8): B01J8/00C01B3/38C01B3/50C01B3/56
CPCC01B3/38C01B2203/82C01B3/503C01B3/56C01B2203/0233C01B2203/0405C01B2203/043C01B2203/047C01B2203/0475C01B2203/048C01B2203/0485C01B2203/066C01B2203/0816C01B2203/0827C01B2203/1047C01B2203/1058C01B2203/1064C01B2203/107C01B2203/1247C01B2203/1276C01B2203/1288C01B2203/142C01B2203/148C01B3/384
Inventor LOFFLER, DANIEL G.
Owner NU ELEMENT
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